made icon optional and default to empty string & adjust all game instances

lib/data/dto/game.dart

@@ -1,6 +1,6 @@
 import 'package:clock/clock.dart';
-import 'package:uuid/uuid.dart';
 import 'package:tallee/core/enums.dart';
+import 'package:uuid/uuid.dart';
 
 class Game {
   final String id;
@@ -18,10 +18,11 @@ class Game {
     required this.ruleset,
     String? description,
     required this.color,
-    required this.icon,
+    String? icon,
   }) : id = id ?? const Uuid().v4(),
        createdAt = createdAt ?? clock.now(),
-       description = description ?? '';
+       description = description ?? '',
+       icon = icon ?? '';
 
   @override
   String toString() {
@@ -49,4 +50,3 @@ class Game {
     'icon': icon,
   };
 }
-

lib/data/dto/match.dart

@@ -27,8 +27,8 @@ class Match {
     String? notes,
     this.winner,
   }) : id = id ?? const Uuid().v4(),
-        createdAt = createdAt ?? clock.now(),
-        notes = notes ?? '';
+       createdAt = createdAt ?? clock.now(),
+       notes = notes ?? '';
 
   @override
   String toString() {
@@ -38,14 +38,21 @@ class Match {
   /// Creates a Match instance from a JSON object (ID references format).
   /// Related objects are reconstructed from IDs by the DataTransferService.
   Match.fromJson(Map<String, dynamic> json)
-      : id = json['id'],
-        createdAt = DateTime.parse(json['createdAt']),
-        endedAt = json['endedAt'] != null ? DateTime.parse(json['endedAt']) : null,
-        name = json['name'],
-        game = Game(name: '', ruleset: Ruleset.singleWinner, description: '', color: GameColor.blue, icon: ''), // Populated during import via DataTransferService
-        group = null, // Populated during import via DataTransferService
-        players = [], // Populated during import via DataTransferService
-        notes = json['notes'] ?? '';
+    : id = json['id'],
+      createdAt = DateTime.parse(json['createdAt']),
+      endedAt = json['endedAt'] != null
+          ? DateTime.parse(json['endedAt'])
+          : null,
+      name = json['name'],
+      game = Game(
+        name: '',
+        ruleset: Ruleset.singleWinner,
+        description: '',
+        color: GameColor.blue,
+      ), // Populated during import via DataTransferService
+      group = null, // Populated during import via DataTransferService
+      players = [], // Populated during import via DataTransferService
+      notes = json['notes'] ?? '';
 
   /// Converts the Match instance to a JSON object using normalized format (ID references only).
   Map<String, dynamic> toJson() => {